The present invention relates to a bifunctional phenylene ether oligomer (to be sometimes referred to as xe2x80x9cPEOxe2x80x9d hereinafter). More specifically, it relates to a curable resin composition having a phenolic hydroxyl group, a thermosetting functional group or the like at each terminal, its cured product, its use and a process for the production thereof. According to the present invention, there are produced a thermosetting resin or a photocurable resin and its intermediate product each of which is suitable for use in electronics fields requiring a low dielectric constant, a low dielectric loss tangent and high toughness and also suitable for various uses such as coating, bonding and molding.
As for materials for use in an electric or electronic field, as the speed of transmission signal increases, a low dielectric constant which decreases a time delay and a low dielectric loss tangent which decreases a loss are desired for utilizing a high-frequency wave (gigahertz band). Further, higher toughness is also desired in order to inhibit the occurrence of microcracks thought to be generated by thermal shock and secure high reliability.
For the above demands, the use of engineering plastic such as polyphenylene ether (PPE) is proposed. PPE has excellent high frequency properties. On the other hand, known problems of PPE are that it is poor in compatibility with a thermosetting resin such as an epoxy resin or a cyanate resin, that it has a high melt viscosity so that molding processability is poor, and that a solvent in which it is soluble is limited to an aromatic hydrocarbons solvent such as toluene, benzene or xylene and an halogenated hydrocarbon solvent such as methylene chloride or chloroform so that workability is poor.
For improving compatibility, a method of improving compatibility by blending PPE with a different resin as a compatibilizing agent is discussed and the pseudo IPN structuralization of a cyanate resin is also discussed (JP-A-11-21452, etc.). However, the problems of molding processability and heat resistance have not been solved yet. Further, a method of converting a high molecular PPE into a low molecular compound is discussed for improving moldability. For example, there are known a method in which a high molecular PPE and a bivalent phenol are redistributed in the presence of a radical catalyst (JP-A-9-291148, etc.) and a method in which a bivalent phenol and a monovalent phenol are subjected to oxidation polymerization (JP-B-8-011747). In each of the above methods, a high molecular substance is presence so that it is impossible to obtain a bifunctional low molecular oligomer effectively.
Further, an epoxy acrylate compound has been widely used as raw materials for various functional high molecular materials such as a photosensitive material, an optical material, a dental material, an electronic material and crosslinking agents for various polymers. However, since higher performances are being required in these application fields in recent years, physical properties required as a functional high molecular material become severer increasingly. As such physical properties, for example, heat resistance, weather resistance, low water absorptivity, high refractive index, high fracture toughness, low dielectric constant and low dielectric loss tangent are required. Until now, these required physical properties have not been necessarily satisfied. For example, concerning the production of a printed wiring board, it is known that an epoxy acrylate compound is used for a photo solder resist used as a permanent mask. As a resist material like above, there are known a novolak type epoxy acrylate compound disclosed in JP-A-61-243869, a bisphenol fluorene type epoxy acrylate compound disclosed in JP-A-3-205417 and acid-modified products of these epoxy acrylate compounds. In a use for a printed wiring board, heat resistance in an immersion in a solder bath is demanded. When the heat resistance is insufficient, swelling or peeling off of a resist film occurs, which causes defectives. In compliance with an increase in the speed of transmission signal, recently, in addition to the above-mentioned heat resistance, a lower dielectric constant which decreases a time delay and a lower dielectric loss tangent which decreases a loss are desired for utilizing a high-frequency wave (gigahertz band). However, a conventional epoxy acrylate compound is insufficient in dielectric characteristic corresponding to a high-frequency wave. For this reason, a novel epoxy acrylate compound which satisfies the above requirements is demanded.
On the other hand, as a thermosetting resin, there are known a polyphenylene ether modified epoxy resin, a thermosetting type polyphenylene ether and the like. A conventional thermosetting resin has problems with regard to workability, moldability, heat resistance or the like. That is, problems are that, when a varnish is prepared by using the conventional thermosetting resin, a solvent is limited, and that due to a high melt viscosity, a high multilayer formation can not be carried out and a high temperature and a high pressure are required at a molding time. Further, a cyanate ester resin is known as a thermosetting resin having excellent dielectric characteristic and excellent moldability. However, when a cyanate ester resin alone is used, a cured product is too hard and is fragile so that it has a problem with regard to adhesive property and solder resistance. When a cyanate ester resin is used in combination with an epoxy resin, the above defects can be covered to some extent. However, it is difficult to cope with requirements of lower dielectric characteristics for laminates, which requirements are becoming severer, by using a conventional cyanate ester resin in combination with a conventional epoxy resin. Further, the coexistence of lower dielectric characteristics and flexibility is difficult.
Concerning a semiconductor device, an epoxy resin composition is generally used for sealing electronic parts such as a semiconductor. The above-mentioned epoxy resin composition is composed of various epoxy resins such as a cresol novolak type epoxy resin, a bisphenol A type epoxy resin and a biphenyl type epoxy resin, a curing agent therefor, an inorganic filler, a curing accelerator as required, a coupling agent, a releasing agent, a coloring agent and the like.
In compliance with recent requirements for a decrease in size or a decrease in thickness, the formation technique of the above electronic parts is being changed from a conventional through hole mounting method (DIP: dual inline package, etc.) to a surface mounting method (SOP: small outline package, QFP: quad flat package, etc.). In the surface mounting method, since a semiconductor device is treated at a high temperature (for example 210xc2x0 C.xcx9c260xc2x0 C.) at a solder reflow or the like at a mounting time, a high temperature heat is applied to the entire semiconductor device. In this case, problems such as the occurrence of cracks in a sealing layer formed of the above epoxy resin composition and a large decrease in humidity resistance are apt to occur. For example, when a thin sealing layer having a thickness of 2.0 mm or less is used, cracks are apt to occur at the time of a solder reflow. In view of a further improvement in physical properties and an increase in a signal transmission speed in a chip circuit, it is demanded to carry out a sealing with a sealing layer having a lower dielectric constant.
Countermeasures against the above are proposed. One countermeasure with respect to handling is that a semiconductor device before mounting is packaged in a moisture-proof case. As an improvement in a sealing epoxy resin composition, for example, JP-A-1-108256 discloses a sealing material containing a biphenyl type epoxy resin and JP-A-64-24825 discloses a sealing material containing an epoxy resin and a polyphenylene ether type resin in combination.
Further, a (meth) acrylate compound have been widely used as raw materials for various functional high molecular materials such as a photosensitive material, an optical material, a dental material, an electronic material and crosslinking agents for various polymers. However, since higher performances are being required in these application fields in recent years, physical properties required as a functional high molecular material become severer increasingly. As such physical properties, for example, heat resistance, weather resistance, low absorptivity, high refractive index, high fracture toughness, low dielectric constant and low dielectric loss tangent are required. Until now, these required physical properties have not been necessarily satisfied.
It is an object of the present invention to provide a bifunctional phenylene ether oligomer which is a resin having the excellent electric characteristics and toughness of PPE and improved in compatibility with a different resin and moldability and which is soluble in a general-purpose ketone solvent and has a PPE structure whose terminal phenolic hydroxyl groups are easy to modify, and a thermosetting resin obtained from the above oligomer.
It is another object of the present invention to provide a novel epoxy acrylate compound and a curable resin composition which have excellent heat resistance and have a low dielectric constant and a low dielectric loss tangent.
It is further another object of the present invention to provide, in a printed wiring board material field, a thermosetting resin composition excellent in dielectric characteristic and also excellent in molability, heat resistance, etc., a laminate obtained by using the thermosetting resin composition and a printed wiring board obtained by the thermosetting resin composition.
It is still another object of the present invention to provide a sealing epoxy resin composition capable of giving a sealing layer which is free from the occurrence of cracks when it is exposed to a high temperature, such as a temperature in a solder reflow, and has a low dielectric constant.
It is still further another object of the present invention to provide, in a printed wiring board material field, a thermosetting resin composition which copes with the severe requirement of low dielectric characteristics and has flexibility, a laminate obtained by using the above thermosetting resin composition and a printed wiring board obtained by using the above thermosetting resin composition.
It is furthermore another object of the present invention to provide a novel (meth)acrylate compound and a curable resin composition which have excellent heat resistance and have a low dielectric constant and a low dielectric loss tangent.
According to the present invention 1, there is provided a bifunctional phenylene ether oligomer of the formula (1), obtained by oxidation polymerization of a bivalent phenol of the formula (2) and a monovalent phenol of the formula (3),
H"Brketopenst"Oxe2x80x94Y"Brketclosest"a"Parenopenst"Oxe2x80x94Xxe2x80x94O"Parenclosest""Brketopenst"Yxe2x80x94O"Brketclosest"bHxe2x80x83xe2x80x83(1) 
HOxe2x80x94Xxe2x80x94OHxe2x80x83xe2x80x83(2) 
Yxe2x80x94OHxe2x80x83xe2x80x83(3) 
(wherein xe2x80x94Xxe2x80x94 is represented by the formula (2xe2x80x2), 
in which R2, R3, R4, R8 and R9 may be the same or different and are a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group, R5, R6 and R7 may be the same or different and are a hydrogen atom, a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group,
Yxe2x80x94Oxe2x80x94 is represented by the formula (3), 
in which R10 and R11 may be the same or different and are a halogen atom or an alkyl group having 6 or less carbon atoms or a phenyl group, R12 and R13 may be the same or different and are a hydrogen atom, a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group,
provided that Yxe2x80x94Oxe2x80x94 is an arrangement of one kind of structure defined by the formula (3xe2x80x2) or a random arrangement of at least two kinds of structures defined by the formula (3xe2x80x2), and each of a and b is an integer of 0 to 300, preferably 0 to 100, more preferably 0 to 50, provided that at least either a or b is not 0),
R2, R3, R4, R8, R9, R10 and R11 in the formula (2) and the formula (3) being required not to be a hydrogen atom.
According to the present invention 2, further, there is provided a thermosetting resin represented by the formula (4), 
wherein xe2x80x94Xxe2x80x94, Yxe2x80x94Oxe2x80x94, a and b are as defined in the formula (1), Z is an organic group having one or more carbon atoms and may contain an oxygen atom, and each of c and d is an integer of 0 or 1.
According to the present invention 2, further, there is provided a thermosetting resin, as a preferable thermosetting resin, according to the above, wherein xe2x80x94Xxe2x80x94 in the 5 above formula is represented by the formula (5) and Yxe2x80x94Oxe2x80x94 has an arrangement structure of the formula (6) or the formula (7) or a random arrangement structure of the formula (6) and the formula (7). 
According to the present invention 3, further, there is provided an epoxy acrylate compound represented by the formula (8), 
wherein R13 is a hydrogen atom or a methyl group, xe2x80x94Xxe2x80x94, Yxe2x80x94Oxe2x80x94, a and b are as defined in the formula (1), Z, c and d are as defined in the formula (4) and n is an integer of 0 to 10.
According to the present invention 3, further, there is provided an epoxy acrylate compound according to the above, wherein xe2x80x94X is represented by the formula (5) recited above, and Yxe2x80x94Oxe2x80x94 has an arrangement structure of the formula (6) recited above or the formula (7) recited above or a random arrangement structure of the formula (6) and the formula (7).
According to the present invention 3, further, there are provided an acid-modified epoxy acrylate compound of the above epoxy acrylate compound, a curable resin composition containing these, and a cured product obtained by curing the above composition.
According to the present invention 4, further, there is provided an epoxy resin composition for laminates, comprising a curing agent and a phenylene ether oligomer compound having a number average molecular weight of 700 to 3, 000 and having an epoxy group at each terminal, represented by the formula (9), 
wherein xe2x80x94Xxe2x80x94, Yxe2x80x94Oxe2x80x94, a and b are as defined in the formula (1), Z, c and d are as defined in the formula (4), and n is an integer of 0 to 10.
According to the present invention 4, further, there is provided a resin composition for laminates, wherein the above resin composition further contains a cyanate resin.
According to the present invention 4, further, there is provided prepreg, a laminate, or a printed wiring board obtained by using the above epoxy resin composition for laminates.
According to the present invention 5, further, there is provided a sealing epoxy resin composition containing the epoxy resin composition recited above and further containing as ingredients an epoxy resin and an inorganic filler.
According to the present invention 6, further, there is provided a resin composition for laminates, containing as an ingredient a phenylene ether oligomer cyanate compound having a number average molecular weight of 700 to 3,000 and having a cyanate group at each terminal, represented by the formula (10), 
wherein xe2x80x94Xxe2x80x94, Yxe2x80x94Oxe2x80x94, a and b are as defined in the formula (1) and Z, c and d are as defined in the formula (4).
According to the present invention 6, further, there is provided a resin composition for laminates according to the above, which contains the cyanate compound of the formula (10) and further contains a different cyanate ester resin and an epoxy resin.
According to the present invention 7, further, there is provided a (meth)acrylate compound represented by the formula (11), 
wherein Xxe2x80x94, Yxe2x80x94Oxe2x80x94, a and b are as defined in the formula (1), Zxe2x80x2 is an organic group which have no OH group in a side chain and has one or more carbon atoms and which may contain an oxygen atom, c and d are as defined in the formula (4), and R15 is a hydrogen atom or a methyl group.
According to the present invention 7, further, there is provided a curable resin composition containing the above (meth)acrylate compound.